1. Field of the Invention
The present invention relates to a turntable that is provided in a disc-drive for rotationally driving a disc-like recording medium, such as an optical disc or a magneto-optical disc, and recording and/or reproducing information, as well as to a method of manufacturing the turntable, a disc chucking apparatus that uses the turntable, and a disc-drive that uses the turntable.
2. Description of the Related Art
Information is usually recorded onto and reproduced from a disc-like recording medium like an optical disc (e.g., a CD (Compact Disc), CD-ROM (Compact Disc-Read Only Memory), or a DVD (Digital Video/Versatile Disc)), and a magneto-optical disc by loading a disc into a disc-drive. In a disc-drive, a disc-like recording medium in the form of an optical disc is placed upon a turntable that is attached to a rotational shaft of a spindle motor, the disc is chucked, and the disc is rotationally driven while an optical head of an optical pickup apparatus irradiates laser light at the information recording surface of the optical disc, with recording or reproduction being performed for the optical disc as the optical pickup apparatus is moved in the radial direction.
FIG. 8 shows a conventionally known disc chucking apparatus and a disc-drive. The disc-drive 1 shown in FIG. 8 is composed of a box-like main chassis 2 that has openings in the top and the front surfaces, a disc tray 3 with a disc mounting part 3a that is moved in and out of the front opening of the main chassis 2 and on which an optical disc D is placed, a base holder 4 that is kept in a depressed part in the main chassis 2 and is supported so as to be able to swing, and a base unit 5 that is elastically supported by the base holder 4.
The base unit 5 includes a spindle chassis 7 that supports a turntable 6 to which the optical disc D is attached, so that the turntable 6 is freely rotatable and a pickup chassis 9 that supports an optical pickup apparatus 8, which reproduces information from the optical disc D that has been attached to the turntable 6, in a way such that the optical pickup apparatus 8 is able to move. The spindle chassis 7 and pickup chassis 9 compose a base chassis 10.
The pickup chassis 9 of the base unit 5 is supported in approximately the center of the spindle chassis 7, so as to be freely rotatable, while a rear end of the base holder 4 that supports the base unit 5 is rotatably supported by the main chassis 2. A cam pin 11 that is provided at the front end of the base holder 4 engages a chuck cam mechanism 12 disposed at the front of the main chassis 2, so that the base holder 4 is rotated up and down by the movement of the chuck cam mechanism 12 with the support at the rear end of the base holder 4 as the pivot.
A mounting part 6a on which the periphery of the center hole d of the optical disc D is placed and a disc engaging part 6b in the form of a truncated cone that engages the center hole d are integrally formed in the turntable 6 that is supported by the spindle chassis 7, with a ring-shaped magnet 13 being inserted along with a ring-shaped yoke plate 14 onto the disc engaging part 6b. A central shaft part of this turntable 6 engages and is fixed to rotational shaft 15a of a spindle motor 15 that is fixed to the spindle chassis 7.
A chuck holder 16 is attached to the top of the main chassis 2 so as to cross the disc tray 3 above the disc tray 3. A chucking plate 17 that faces the turntable 6 is supported by the chuck holder 16, so as to be capable of swinging and rotating.
When the disc-drive 1 of the above construction is not in use, the base unit 5 is moved downwards. In other words, the front of the base holder 4 is rotated downwards at an angle about the rear support, with the turntable 6 that is supported by the spindle chassis 7 being positioned below the disc tray 3.
In order to reproduce an optical disc D, the disc tray 3 is first ejected from the main chassis 2 by an eject operation. After an optical disc D has been placed on the disc mounting part 3a, a loading operation is performed and the disc tray 3 is retracted back into the main chassis 2, with the base holder 4 being rotated upwards into an approximately horizontal state via the cam pin 11 due to the chuck cam mechanism 12 being driven. Since the base holder 4 is moved upwards in this way, the turntable 6 enters the opening 3b in the disc tray 3 from below, with the disc engaging part 6b engaging the center hole d of the optical disc D that has been placed on the disc tray 3 and the periphery of the center hole d being mounted on the disc mounting part 6a of the turntable 6. The mounting part 6a of the turntable 6 lifts up the optical disc D slightly, with the chucking plate 17 that is supported by the chuck holder 16 being held by the magnet 13 that is inserted on the disc engaging part 6b of the turntable 6.
As a result, the optical disc D is chucked by being supported on both sides by the turntable 6 and the chucking plate 17 so that the optical disc D is coupled with the turntable 6 in the rotational direction and is rotated at a predetermined speed by the driving force of the spindle motor 15, with reproduction being performed by predetermined movement of the optical pickup apparatus 8.
In a disc-drive 1 of the above construction, the turntable 6 of the rotational driving mechanism for the optical disc D is constructed of a ring-shaped magnet 13 and a ring-shaped yoke plate 14 that are inserted, as shown in FIG. 11, onto the disc engaging part 6b, which engages the center hole d of the optical disc D and is in the form of a truncated cone, so as to surround the center shaft portion of the disc engaging part 6b. With this construction, the optical disc D is chucked as shown in FIG. 8 between a chucking plate 17 and the magnet 13 and yoke plate 14.
The magnet 13 and the yoke plate 14 have to be inserted onto the disc engaging part 6b concentrically with the central shaft part of the turntable to prevent eccentric rotation of the turntable 6.
For the above reason, when the magnet 13 and the yoke plate 14 are inserted and the turntable 6 is molded, it is necessary to position the magnet 13 and the yoke plate 14 accurately. As shown in FIG. 11, this is conventionally achieved by arranging molding pins 18 for positioning the magnet 13 and the yoke plate 14 in the horizontal direction at at least three positions around the circumferential surface of the disc engaging part 6b during the molding of the turntable 6. The turntable 6 is then molded with the magnet 13 and the yoke plate 14 being positioned in the horizontal direction by these molding pins 18.
However, with a turntable 6 that has been molded as described above, the withdrawal holes 19 of the molding pins 18 are exposed to the circumferential surface of the disc engaging part 6b, as shown in FIGS. 9 and 10. When a disc chucking operation is performed with this turntable 6, as shown in FIGS. 12A and 12B, the turntable 6 rises from a position below and at an angle to the optical disc D, so that the disc engaging part 6b engages the center hole d of the optical disc D.
At this point, the sloped circumferential surface of the disc engaging part 6b, which composes the disc sliding surface 6c, comes into sliding contact with the inner circumferential edge of the center hole d, wherein the withdrawal holes 19 of the molding pins 18 ends up being on the disc sliding surface 6c for the inner circumferential edge of the center hole d of the optical disc D to get caught on the edges of the withdrawal holes 19 of the molding pins 18 that are positioned in the disc sliding surface 6c (i.e., the circumferential surface of the disc engaging part 6b), leading to potential problems during the chucking of the optical disc D. In particular, if burrs and rough edges remain at the peripheral edges of the withdrawal holes 19 of the molding pins 18 during molding, there is a further increase in the likelihood of such problems occurring.
The present invention was implemented in view of the problems described above and has an object of forming a turntable that is provided in a disc chucking apparatus or a disc-drive, the turntable being formed with a disc chucking member, which is one of a magnet and a magnetically attracted member, having been inserted onto a disc engaging part and with molding pins for positioning the disc chucking member being arranged so as not to touch the disc sliding surface.
In order to achieve the stated object, the present invention is a turntable that is formed with a disc chucking member, which is one of a magnet and a magnetically attracted member, having been inserted onto a disc engaging part that engages a center hole of a disc and is in the form of a protrusion, the turntable including a plurality of positioning parts for positioning the disc chucking member, the positioning parts being formed in a circumferential surface of the disc engaging part and being formed by providing stepped surfaces that are lower than a disc sliding surface of the circumferential surface of the disc engaging part.
With the turntable of the present invention that has the above construction, the positioning parts for the disc chucking member that is inserted onto the disc engaging unit that engages the center hole of a disc are formed by providing stepped surfaces that are lower than the disc sliding surface on the circumferential surface of the disc engaging part. As a result, the positioning parts do not protrude from the disc sliding surface, and when a disc engages and is mounted on the turntable, the inner circumferential edge of the center hole of the disc smoothly engages and is mounted on the disc sliding surface of the disc engaging part.
Also, the present invention is a method of manufacturing a turntable that is formed by inserting a disc chucking member, which is one of a magnet and a magnetically attracted member, onto a disc engaging part that engages a center hole of a disc and is in the form of a protrusion, including the steps of: arranging molding pins by (i) molding pins at stepped parts, which are lower than the molding surface for a disc sliding surface, at a plurality of positions on a mold corresponding to a circumferential surface of the disc engaging part and (ii) passing the molding pins through the stepped parts and molding the turntable with the disc chucking member having been positioned.
A turntable that is formed using the above method has positioning parts for the disc chucking member formed in stepped parts that are lower than the disc sliding surface of the circumferential surface of the disc engaging part, so that the positioning parts do not protrude from the disc sliding surface, and when a disc engages and is mounted on the turntable, the inner circumferential edge of the center hole of the disc smoothly engages and is mounted on the disc sliding surface of the disc engaging part.
A disc chucking apparatus according to the present invention is constructed so that a disc is chucked by being held between the above turntable and a chucking plate.
With a disc chucking apparatus of the above construction, the positioning parts for the disc chucking member are formed in stepped parts that are lower than the disc sliding surface of the circumferential surface of the disc engaging part, so that the positioning parts do not protrude from the disc sliding surface, and when a disc engages and is mounted on the turntable, the inner circumferential edge of the center hole of the disc smoothly engages and is mounted on the disc sliding surface of the disc engaging part.
The disc-drive of the present invention is constructed so as to perform recording and/or reproduction by rotationally driving a disc using a spindle motor that has the turntable described above.
With a disc-drive of the above construction, the positioning parts for the disc chucking member are formed in stepped parts that are lower than the disc sliding surface of the circumferential surface of the disc engaging part, so that the positioning parts do not protrude from the disc sliding surface, and when a disc engages and is mounted on the turntable, the inner circumferential edge of the center hole of the disc smoothly engages and is mounted on the disc sliding surface of the disc engaging part. As a result, favorable recording and/or reproduction can be performed.